Synchronous Digital Hierarchy (SDH) is based on time division multiplexing technology, and provides a time division multiplexing transmission channel of a fixed bandwidth. However, with the rapid development of data communication and in view of the burst feature and unpredictability of data services, currently applied SDH technology is less and less adaptable to explosively growing data services.
In order to meet the requirements of explosively growing data services, the International Telecommunications Union-Telecommunications (ITU-T) integrated some features of SDH technology with the bandwidth extension technology of the Dense Wavelength Division Multiplexing (DWDM) to formulate the OTN standard series. The OTN technology includes electrical-layer and optical-layer technical specifications, and provides a Tandem Connection Monitoring (TCM) processing method and a Forward Error Correction (FEC) method to schedule and manage high-capacity services flexibly.
Currently, in order to transmit high-capacity data, more and more services use an OTN to transmit data. For example, 100G Ethernet, representative of the mainstream Metropolitan Area Network (MAN) technologies, adapts to the signals transmitted on the OTN in the following two methods.
The first method adapts the 100GE signals for a Virtual Concatenation Group (VCG) composed of 11 Optical channel Payload Units (OPUs) whose rate level is 2 (namely, the rate is 10 Gbps) (OPU2-11v). More specifically, the adaptation may include, decoding the 100GE signals, encapsulating the decoded signals through a General Framing Procedure (GFP), mapping the encapsulated signals to 11 OPU2 virtual concatenation units, and sending the signals to the OTN for transmitting.
The second method adapts the 100GE signals for a VCG composed of three OPUs whose rate level is 3 (namely, the rate is 40 Gbps) (OPU3-3v). Using the second method, the adaptation may include, decoding the 100GE signals, encapsulating the decoded signals through a GFP, mapping the encapsulated signals to three OPU3 virtual concatenation units, and sending the signals to the OTN for transmitting.
The aforementioned methods, however, have defects. For example, in the method which adapts the 100GE signals for the OPU2-11v, the signals of a 100 G bandwidth are adapted for an 11*2.5 G bandwidth, thus wasting a bandwidth of about 9.95 G. Moreover; the transmission cost is high because 11 chromatic wavelengths are occupied. Further, in the method which adapts the 100GE signals for the OPU3-3v, the signals of a 100 G bandwidth are adapted for a 3*40 G bandwidth, thus causing enormous bandwidth waste of about 20.45 G and reducing the transmission efficiency.